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Rear brakes locking up

Discussion in 'Cal 1400 8V' started by Matt Russell, Jun 10, 2021.

  1. Matt Russell

    Matt Russell Just got it firing!

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    Any idea what would cause them to lock up. Initially I thought there might be an issue with the transmission, several times this week I have had to rock the bike back and forth a few times to be able to move it that was my thought until today when riding back home it happened again and this time while riding, I got home and realized the brake pads almost gone and well over heated. I am going to take it to the shop in a couple of weeks to get it fixed but any idea why they would lock up
     
  2. BrianR

    BrianR Cruisin' Guzzisti GT Famiglia

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    It could be debris between the foot lever and the hanger, preventing the lever from returning or the return spring broken, or the pivot being corroded, or the slider pins all rusted up or the pistons being corroded. Have you dropped the bike on that side? It could be numerous things and smarter people than me will suggest other options. Take a picture of the caliper from underneath and from the side as well as the disc and the lever with spring and pivot bolt. That would all help.
    PS, what does your avatar stand for?
     
  3. Matt Russell

    Matt Russell Just got it firing!

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    Bikes never been dropped, I plan on spraying some penetrating oil in the morning around the lever. You might be right on that when I tapped the rear a few times it freed itself. As for the avatar 9 12 = I L our colors are white and gold, the center is the Hellfire 8
     
  4. sir fred

    sir fred Cruisin' Guzzisti

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    I had the same problem.
    The rear brake would drag and overheat the caliper. I checked out any debris that might affect the pedal. I sprayed WD40 on to the cylinder plunger..Took the brakes apart , lubed the guide pins, bled the brake, made a heat shield for the master cylinder...still occurred.

    I found a reply on a forum where the writer told of this being a problem on a BMW he once had.
    He said the caliper cups were cocking as the pads wore.

    I took the pads out. Cleaned the caliper. Pressed the caliper cups in all the way and replaced with new pads.
    No problem since and I will change the rear pads more frequently now. Probably every other rear tire change or 12k miles. Even if the pads look good.
    I am just about ready for a new tire.25k miles on bike.
    I use Avon V91/92 tires. getting about 7k/rear tire now. They are lasting longer than the previous V71/72s.
     
  5. scottmastrocinque

    scottmastrocinque Scott Mastrocinque GT Famiglia

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    Must be the season...

    This is related to your question:

    https://www.guzzitech.com/forums/threads/rear-brake.21541/#post-173119

    Also, as a matter of courtesy, always state the year, and model of your motorcycle that you are asking questions about. The current mileage is also very helpful.

    I would guess that either your pistons are corroded and not retracting fully, or the brake fluid reservoir is too full, thereby not allowing the excess fluid to return to the reservoir and release the pressure on the pads themselves.

    Do not continue to ride the bike like this. It is completely unsafe until you discover why the brakes are refusing to release.

    Photos are always very helpful as well. I am concerned that you have glazed the pads from extreme heat and maybe even warped your rear rotor. If after resolving this issue, you feel pulsing at the pedal when applying the brake, you will know that you warped the rotor for sure.
     
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  6. Matt Russell

    Matt Russell Just got it firing!

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    I didn't think about that but that would explain exactly why rocking the bike would free them.
     
  7. Matt Russell

    Matt Russell Just got it firing!

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    Well I was finally able to get it into the shop today and have them do a look and replace the pads. There was no issue found which would make it completely possible and very likely that it was the thin pads that caused one of the pistons to go cockeye and lock the brakes. On a side note I did find a shop really close that works on the bikes
     
    John L likes this.
  8. scottmastrocinque

    scottmastrocinque Scott Mastrocinque GT Famiglia

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    As far as I know, in my whole life of working on motorcycles, I believe this to be impossible!

    Brake pistons are precision machined pieces, which due to the nature of the fact that they direct hydraulic pressure to initiate braking forces, they must therefore have extremely tight tolerences.

    There is no way for them to become crooked or cockeyed.
     
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  9. sir fred

    sir fred Cruisin' Guzzisti

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    There is if quality control slips.
    ALL mechanical items are subject to quality control. ALL.

    My worn brake pads were the problem.
    I have contemplated purchasing a new caliper but changing the pads more frequently has alleviated the binding.
    I may have not worked as extensively on mc's as you but I worked as a model maker for a major automotive supplier for product engineering and fully understand machining, tolerances and what happens when products go in to production.
     
    Last edited: Jun 25, 2021
  10. Tracey

    Tracey Just got it firing! GT Contributor

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    I had a similar problem on my 2014 Stelvio. Replaced the master cylinder / hydraulic pump. Fresh pads, fluid, clean and lube all parts. Problem solved. I’m my opinion, brakes are so important I don’t take any half measures.
    Respectfully Submitted
     
  11. Matt Russell

    Matt Russell Just got it firing!

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    Maybe cockeye wasn't the best choice of words. The front piston on the rear caliper was stuck then and the pads were as thin as could be.
     
  12. scottmastrocinque

    scottmastrocinque Scott Mastrocinque GT Famiglia

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    This is not about quality control, it's about the required physical clearance that would need to exist for a brake caliper piston to shift cockeyed. If you were a mechanic you would understand that the caliper would not function at all as the hydraulic fluid would immediately squirt out of the un-round hole under pressure.

    You can search high and low and I promise you that you will never find a piston in a brake caliper that is cockeyed. Never. It's not possible by the very nature of the design.

    For example, take a piece of pipe, place a round piece of metal in it that fits and moves freely through the pipe but isn't perfectly snug and sealed with a rubber seal. Hold that piece in the pipe and pour water in the other end. The water will run out very quickly. Try to let the piece out of the pipe to the point of almost being out, and try to shift it left or right. Again, pour water in the other end of the pipe and it will run out immediately.

    In order for the hydraulic system to exist and function in the first place, there can be no slop, no slack, no clearance. Period.

    A move visual representation is the butterfly valve in an intake. It's round and fills the hole precisely. Then, it is cracked open ever so slightly to allow the bike to breath an air/fuel mixture into the intake. If you take that circular disk and project it in your mind to be a solid, you can easily see how it would be impossible to move into a cocked position as it would be constrained by the throttle body circular shape which would block it.

    Correct.

    You can search high and low and I promise you that you will never find a piston in a brake caliper that is cockeyed. It's simply impossible.
     
    Last edited: Jun 25, 2021
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  13. BrianR

    BrianR Cruisin' Guzzisti GT Famiglia

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    Even my cackhandedness has never been able to cockeye a piston. After two beers, I'm using cockeye as a verb;);)
     
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  14. BrianR

    BrianR Cruisin' Guzzisti GT Famiglia

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    I should add, two beers at 30C at 2125 in Mission BC with the temp expected to reach 40C for the next 5 days. Beer, water, beer, repeat ad hoc:rock::rock:
     
  15. sir fred

    sir fred Cruisin' Guzzisti

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    I'm not twelve years old and I don't get upset by semantics.
    Been around a long time and fixed many things....LOL!
     
  16. scottmastrocinque

    scottmastrocinque Scott Mastrocinque GT Famiglia

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    I apologize if you feel that I implied you were 12.

    This is not remotely about semantics. It is about engineering principles and science and the realities of how a hydraulic system works.

    Moving on…
     
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  17. sir fred

    sir fred Cruisin' Guzzisti

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  18. Matt Russell

    Matt Russell Just got it firing!

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    But it was the case whether an engineering degree or not. I appreciate the helpful responses well the one of them the others not so much. I asked the question for answers ahead of getting it looked at that was my fault but the comments from those who weren't so helpful please keep that to yourself. So what happened defied your knowledge base so feel bad because I don't care, we can all claim to know the exact knowledge of any given subject without any proof whatsoever , but I am not the one to try being a smart ass to. Thanks for the help and the laugh
     
  19. tobinh

    tobinh Cruisin' Guzzisti GT Famiglia

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    what the heck is going on in this thread.

    it is very literally impossible for a piston to be 'cockeye' in the bore of a caliper.

    just... look at one. the reason why will be very obvious!

    what a thing to argue!
     
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  20. Moto-Uno

    Moto-Uno Cruisin' Guzzisti

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    Without actually seeing the caliper assembly , this is kinda hard to really visualize . The sealing O rings
    can make up for some poorly fitting parts . So called "cockeyed" pistons I haven't seen since the early
    70's in HD rear brake calipers . You'd of have to had worked on them to see how that may of been possible.
    But that's pretty irrelevant in reference to anything as modern as the brakes we have today . Sticking
    or seized pistons due to water accumulating in the brake fluid is however a real possibility . But I too
    would like to see some pics of the pistons being out of alignment in the bores . Peter
     
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